Indirectly heated cathode, for cathode ray tubes in particular



Sept. 6, 1955 K. GOSSLAR INDIRECTLY HEATED CATHODE, FOR CATHODE RAYTUBES IN PARTICULAR Filed April 2, 1955 IN VEN TOR.

KARL 60.7.71 A1,?

ATTORNEY United States Patent 0 INDIRECTLY HEATED CATHODE, FORCA'ilI-IQDE RAY TUBES IN PARTICULAR Karl Gosslar, ()beresslingen,Germany, assignor to international Standard Electric (lorporation, NewYork, N. Y., a corporation of Delaware Application April 2, 1953, SerialNo. 346,455 Claims priority, application Germany April 8, 1952 4 Claims.(Cl. 313-270) In a previously proposed structure a device has beendescribed for insuring the mutual spacing between a rodshaped indirectlyheated cathode and the first electrode, immediately neighboured to thelatter, of an electronoptic system for cathode ray tubes. According tothis structure the cathode, near its emitting surface, is fastened in aninsulating body and between the other end of the cathode and theinsulating body there is an arrangement of springs or a springpreventing variation of the spacing between the edge of the insulatingbody which contacts the first electrode of the electron-optic system andthe point or the emitting surface of the cathode, due to thermalexpansion of the elements.

The present invention presents a particularly simple and inexpensivedesign example of a device for securing of the mutual spacing between acathode and the nearest electrode. This is accomplished in such a mannerthat the cathode arranged in an insulating body is provided at its lowerend with a flanged rim wherein is fitted the one end of a conicallywound spring whose other end presses against the insulating body whereinthe cathode is seated. This arrangement offers the advantage thatthrough a simple structure firm fitting of the cathode is attained withonly slight heat leakage.

The invention will now be explained in greater detail with reference tothe attached drawings illustrating a structural example of a cathodeassembly incorporating this invention.

Numeral 1 designates the insulating body, within which the cathode 2 isseated, with its upper part resting on the front face of this insulatingbody. Numeral 3 signifies the flanged rim of the cathode 2. The cathode2 extends through the hole 4 in the insulating body. A conical helixspring is represented by 5. To reduce heat leakage, the hole 4, providedfor receiving the cathode, may be surrounded by further holes 6, in theinsulating'body.

These holes increase the thermal resistance of the insulating body inthe vicinity of the cathode. Heat leakage is further reduced by makingthe contact surfaces between the cathode and the insulating body assmall as possible. This may be achieved by making the hole in theinsulating body triangular, square shaped or polygonal. Thus thesupporting rim of the cathode will not be in contact with the insulatingbody throughout its entire circumference. The hole 4 in the insulatingbody may also be designed as a triangular, square shaped or polygonaltruncated pyramid, in order to keep down temperature drain as much aspossible while securing good fitting of the cathode. In order to secureproper fitting of the helical spring,'the insulating body may beprovided on its underside with a groove to receive the outer coil of thespring.

What is claimed is: p

1. A structure for securing a cathode electrode in fixed positionregardless of thermal expansion efiects, comprising a rod shaped cathodehaving a first rim at one end near the emitting surface, and a flangedsecond rim provided with an upturned groove at itsother end, said secondrim being integral with and turned up from said rodshaped cathode, aninsulating support member provided with an opening larger than the bodyof said rod but smaller than said first rim on one surface thereof, saidcathode being seated in said opening with said first rim restingon saidone surface, and a conically wound spring mounted in comparison with itssmaller end in the groove on said second rim, and its other end pressingagainst the other surface of said insulating support.

2. A structure according to claim 1, wherein said insulating support isprovided with a groove on said other surface to receive said other endof said spring.

3. A structure according to claim 1, wherein the opening at said onesurface of said support is polygonal in shape, with some of its crossdimensions being greater than the diameter of said first rim, wherebycontact between said rim and said support is not continuous throughoutthe periphery of said rim.

4. A structure according to claim 3, wherein the remainder of saidopening between said first and second surfaces is in the form of atruncated polygonal pyramid.

References Cited in the file of this patent UNITED STATES PATENTS

